docs: Install instructions no longer misleading

I mentioned that running plain `cabal install` added the `wasm-verify` executable to your path: that was a lie, which makes me an 嘘つき. You have to do the `cabal install` before the `cabal exec`.

README.md

@@ -30,7 +30,7 @@ From within the project's root folder you can run the following command to build
 ```
 cabal install
 ```
-If you would rather not have it in your path, you can build and execute the program from within the repo folder by running:
+Once that's done, you can build and execute the program from within the repo folder by running:
 ```
 cabal exec -- wasm-verify <the flags you want to use>
 ```